/Engine/Source/Runtime/DeveloperSettings/Public/Engine/PlatformSettings.h
Step 4) Nothing else needed. In your system code, you will just call UMyPerPlatformSettings* MySettings =UPlatformSettingsManager::Get().GetSettingsForPlatform() that will get you the current settings for the active platform, or the simulated platform in the editor.
class UPlatformSettings : public [UObject](API\Runtime\CoreUObject\UObject\UObject)